Method for manufacturing panel assemblies for automobiles

Abstract

Method is disclosed for manufacturing a panel assembly comprised of an inner panel and an outer panel which are welded together at the peripheral portions thereof. The method comprises steps of forming a plurality of raised portions having projections in the inner panel along at least one peripheral portion thereof so that the raised portions project in a direction opposite to the outer panel, folding a peripheral portion of the outer panel over the peripheral portion of the inner panel so that the peripheral portion of the outer panel covers the raised portions in the inner panel, applying anvils to the outer panel at portions corresponding to the raised portions and applying welding electrodes to the peripheral portion of the outer panel which is folded over the raised portions of the inner panel so as to depress the peripheral portion of the outer panel to the raised portion simultaneously applying a welding current in series through at least two of the welding electrodes for welding the peripheral portion of the outer panel to the raised portion of the inner panel. The process is effective to prevent thermal deformations and depression marks on the outer panel.

We claim: 
     
       1. Method for manufacturing a panel assembly comprised of outer and inner panels, said method comprising the steps of: forming the inner panel along at least one peripheral portion thereof with a plurality of raised portions raised in one direction;   forming each of raised portions with at least one projection projecting in said one direction;   placing the inner panel on the outer panel with the raised portions and the projections directed opposite to the outer panel and with a peripheral portion of the outer panel extending beyond the peripheral portion of the inner panel;   folding the peripheral portion of the outer panel over the peripheral portion of the inner panel so that the peripheral portion of the outer panel is laid over the raised portions of the inner panel;   applying anvils to the outer panel at portions corresponding to the raised portions; and   applying welding electrodes to the peripheral portion of the outer panel at portions corresponding to the raised portions of the inner panel so as to depress the folded peripheral portion of the outer panel to the raised portion while simultaneously applying welding current in series through at least two of the welding electrodes for welding the folded peripheral portion of the outer panel to the raised portions of the inner panel.   
     
     
       2. Method in accordance with claim 1 in which said raised portions are of substantially circular configuration respectively formed with said projections on top surfaces thereof. 
     
     
       3. Method in accordance with claim 1 in which said raised portions are of non-circular configuration each formed with two projections. 
     
     
       4. Method in accordance with claim 3 in which said projections are in the form of elongated ridges. 
     
     
       5. Method in accordance with claim 1 in which said two of the welding electrodes are supplied with welding current in series by being respectively connected to the opposite ends of a secondary winding of a transformer. 
     
     
       6. Method in accordance with claim 1, wherein the peripheral portion of the outer panel is folded over the peripheral portion of the inner panel in such manner that there is substantially no deformation of said raised portions. 
     
     
       7. Method in accordance with claim 1 or 6, wherein the peripheral portion of the outer panel is folded over the peripheral portion of the inner panel in such manner that a portion of the peripheral portion of the outer panel is forced into contact with a portion of the peripheral portion of the inner panel spaced from said raised portions. 
     
     
       8. Method in accordance with claim 1, wherein the welding electrodes are applied to the peripheral portion of the outer panel in such manner that pressure from the welding electrodes is distributed by the raised portions before being transmitted to the outer panel to thereby prevent depression marks on the outer panel.